Japanese Published Patent Application No. 2003-299547 (“JP '547”) and Japanese Published Patent Application No. 2006-26115 (“JP '115”) disclose conventional movable armrest devices. In these armrest devices, the armrest body can freely rotate against a seat frame, and a coil spring is used as a lock spring for locking and unlocking the rotation of the armrest body.
In the armrest device disclosed in JP '547, a lock spring is wound around a stationary shaft that is provided to the seat frame, so that the rotation of the armrest body can be locked and unlocked. The lock spring has a stationary-side hook and a free-side hook. The stationary-side hook is fixed to the armrest body, and the free-side hook moves in the diameter-enlarging direction (the direction for enlarging the diameter of the lock spring) or the diameter-reducing direction (the direction for reducing the diameter of the lock spring). When the free-side hook moves in the diameter-enlarging direction, the lock spring unlocks, and when the free-side hook moves in the diameter-reducing direction, the lock spring locks.
In the armrest device of JP '547, the free-operation part of a ring part makes the free-side hook of the lock spring rotate in the diameter-enlarging direction of the lock spring, and then the free-side engagement part of the free-side hook drops into a slit of a cover part on the side of the armrest body, so that the lock spring unlocks. At the same time, to the extent that the free-side engagement part drops into the slit, the free-side hook moves upward. Thus, the free-side hook loses contact with the free-operation part, and moves in a movement groove, so that the ring part is allowed to rotate. Accordingly, the armrest body can be rotated in the direction that enables the armrest body to be accommodated upright in the seat.
The armrest device disclosed in JP '115 includes an unlocking contact part, an unlocking cam surface, and a switching cam groove. The unlocking contact part contacts the free-side hook of the lock spring, so as to unlock the lock spring. The unlocking cam surface and the switching cam groove become engaged with the free-side hook. In this armrest device, the unlocking contact part rotates the free-side hook of the lock spring in the direction for enlarging the diameter of the lock spring. Thereby, the free-side hook moves onto the unlocking cam surface, and then drops into the switching cam groove. Also, when the unlocking contact part rotates the free-side hook, the guiding cam surface further presses down the free-side hook, and the free-side hook loses contact with the unlocking contact part, so that the free-side hook is allowed to rotate. Therefore, the armrest body can be rotated in the accommodating direction.